Air Springs’ actuators provide ‘missing link’

One of the weakest links in stamping, fabrication and materials handling machinery can be the seals in traditional cylinders used to actuate the equipment involved.

This is especially critical in aggressive atmospheres laden with dust and waste, where such cylinders can clog up and wear prematurely over the millions of cycles for which they must operate.

One simple way to avoid this potential problem is to employ cylinders that totally lack such seals, says pneumatic actuation and isolation specialist Simon Agar.

Mr Agar – who is General Manager of Air Springs Supply Pty Ltd – has more than 20 years experience with Firestone air spring actuators known as Airstrokes.

These highly engineered rubber and fabric air bags are flexible-wall, bellows- type air cylinders, which are ideally suited to engineering of assemblies for high-repetition tasks, for which they are inflated and deflated rapidly to achieve their purpose.

“Traditional cylinder designs contain a piston sliding within a housing of circular cross-section connected to the work by a rod passing through one end of the device, says Mr Agar.

“This design necessitates several guides and seals, which align and seal the sliding surfaces. “These allow a pressurised, contained column of fluid to apply force to the piston.

“An air spring uses none of these components to contain and channel its column of fluid. An air spring contains its column of air in a fabric-reinforced rubber envelope, or bellows. The ends are sealed by bead plates, which are crimped around the bead of the bellows. These plates contain the attachment hardware for the part, normally a blind tapped hole called a blind nut. An air fitting, generally in one bead plate, allows fluid (air) to be introduced into the chamber. The fabric in the side wall of the bellows restricts radial expansion, so pressure is built up, causing axial extension.

“Each style is, in essence, a heavy-duty balloon. Air springs are available in a variety of styles, sporting differing components that control the shape and path of axial extension, but their basic design is the same.”

Air springs can be used instead of more expensive hydraulic systems when applying large forces. Sizes are available from fewer than 80mm to more than nearly 1000mm (3in to 38in) in diameter.

The larger sizes allow force up to 40,000kg each using only 7 bar (100psi) air pressure.

The capital cost of an air spring is normally less than half that of a pneumatic cylinder with equivalent capabilities.

They are also compact and easy to install.

Air springs can be put in a very compact space and extended to more than twice their starting height. This is a tremendous benefit in floor mounted lifting devices and conveyors.